In the end the wife won it. Claire Tomalin last night won the £30,000 Whitbread book of the year award for her biography of Samuel Pepys, just as her husband Michael Frayn had predicted all along.

Frayn, one of her two chief rivals for the overall prize after winning the best novel category himself for his slim and elegant wartime thriller Spies, had threatened to start a bread roll fight if she did win, but in the event no baguettes were thrown.

Ian Hislop, the editor of Private Eye and chairman of the judges, said the rules of the competition forbade a fairy tale ending. "We were not allowed to share the prize so there were no twee 'Ahh, they're married, isn't that lovely' moments," he said.

"Nor did we want to share it with someone she wasn't married to ... Tomalin was the overwhelming winner. It was her against herself really."

The couple, both 69, have kept up an entertaining double act in public since they were shortlisted for the prize, with Frayn insisting from the start that Tomalin's bestselling reappraisal of the 17th century diarist, womaniser and civil servant was the weightier and more deserving of acclaim. She reciprocating by saying she hoped he would win.

But even with such magnanimity, Frayn admitted the unique position London's most distinguished literary couple had found themselves in was playing havoc with their social lives. "I must say, it's a great social difficulty with our friends."

Tomalin, the favourite, generally responded to such exemplary gentlemanly behaviour with guffaws and the occasional, "Oh, do shut up!"

She had previously won the Whitbread first book prize at 40 for her life of the early feminist Mary Wollstonecraft. That victory came a year after her former husband Nick Tomalin, a foreign correspondent with the Sunday Times, was killed by a Syrian rocket on the Golan Heights.

She met Frayn, a former Guardian journalist who is perhaps better known as the writer of such plays as Noises Off and Copenhagen, at a lunch for the Society for the Discouragement of Public Relations, a satirical club set up by her first husband. They married in 1993 after spending the previous 10 years together.

Hislop said there were some dissenting voices but there was "no blood on the carpet. It wasn't unanimous but it was an overwhelming vote. There were a couple of dissenting voices. Everyone thought the Frayn book was beautifully written. Both the novels [Frayn's and Norman Lebrecht's] were about boys during the second world war, and both had their supporters".

While Frayn's Spies was about two boys who suspect one of their mothers may be a German agent, the winner of the first book award, Lebrecht's The Song of Names, focused on the relationship between a swottish only child and a refugee from Warsaw.

The assistant editor of the London Evening Standard had more than one supporter on the panel, Hislop admitted. "Despite the fact that journalists hate each other - and Norman - it's a really good book," he joked. He revealed that he had argued strongly for the poet Paul Farley and his collection, The Ice Age.

But it was the way that Tomalin had "filled in the gaps" in Pepys's eventful and bawdy life that had really impressed the judges. His notoriously frank diaries, first published 150 years after his death, covered only nine years of his life, he said.

"What really impressed our biography panel was that although Tomalin was not first in the race to get a biography out, and she must have watched others ahead of her and wondered if she should go on, hers is the most definitive."